1. The DEC VT05

The VT05 is a very early terminal from Digital Equipment Corp, dating from the early 1970′s. Apart from the great styling on this device the thing that really sticks out is the sheer scale. It was 19″/48cm wide, 12″/30cm high and 30″/76cm deep, weighing in at a mere 55 pounds (25 kilograms)!
Here’s a whole set of pictures (http://hummingbirdsales.com/VT05.html) from someone offering a vt05 for sale. Asking price $3600(!)

2. The DEC VT100

After a severe case of the uglies with the vt52 DEC brought out the VT100,  one of the most successful terminals of all time and in my opinion a nice looking piece of tech.

DEC VT100 terminal

3. The Tektronix 4010

Meet the Tektronix 4010. These terminals were unique in a couple of ways – first off they were graphics terminals and displayed vector based graphics, secondly they used the CRT as data storage (also known as Direct View Bistable Storage Tube (DVBST) , see this wikipedia article for more detail). In the early seventies when these terminals were first released this was a cost effective way of storing data as RAM was prohibitively expensive. The pedestal contains the power supply and associated circuitry.

A very similar but slightly later model 4014. Photo by Jim Rees

More pictures at http://www.selectric.org/tek4010/index.html

4. The HP 266x

Before brushed aluminum Airbooks, before colorful iMacs, before even the endless dull grey boxes of the 80′s and 90′s  – there was Brown…and it was good.
The Hewlett Packard 262x series of terminals were designed for use with HP’s 3000 series mainframes, according to this site (http://www.hpmuseum.net/display_item.php?hw=242), they were nicknamed the ‘ET Head’ terminals. The keyboards (not pictured) were colored in several shades of brown.

Hewlett Packard Terminal

They were replaced by the dull (but very successful) 2392A terminal a couple of years later.

5. Data General Dasher 200

Sporting smooth curves and a color scheme that looks like it would have worked well with Norton/Midnight commander the dasher 200 was Data Generals early terminal for it’s range of mini systems.

data general dasher 200

6. The Lear Siegler ADM-3A

My personal favorite and in my opinion, shoe in for the most stylish dumb terminal there ever was, goes to the Lear Siegler ADM-3A. Integrating both the CRT display screen and the keyboard into one molded plastic shell the ADM-3A still looks great xx years later. It’s a wonder someone hasn’t modded one these and stuffed a modern system or games console inside.

Other ADM-Xs retained similar styling and the Televideo 910 bears more than a passing resemblance. Keen eyed readers will see ADM-3A in the background of the VT-05 video.

Adm3a - Image from Chris Jacobs collection

Hyperterminal is perhaps the terminal emulation software that is most familiar to users of Microsoft operating systems. Beginning with Windows 95 Hyperterminal was distributed with each and every copy of Microsoft Windows up until Windows Vista, when Microsoft discontinued bundling it with their family of operating systems.

Hyperterminal was produced by Hilgraeve Inc, a software developer based in Detroit and while the program’s functionality was very limited compared to commercial competitors (and even some freeware alternatives) a ‘pro’ version was offered to users looking for something a little extra.

So, what did Hyperterminal do?

Hyperterminal was essentially a telnet client supporting VT52/100, ANSI and various videotext variants such as Minitel and Viewdata. It was able to handle TCP/IP or serial/modem connections and was also touted as being a tool for connecting to BBSs. Various types of file transfer, mostly along the lines of Kermit/xModem/zModem and so on, were supported. Microsoft even suggested using Hyperterminal to check and troubleshoot your modem.

Where can I download a copy of Hyperterminal?

Google is your friend. A couple of sites are still hosting versions of Hyperterminal for download, but I can’t vouch for them, so search at your own risk.

On the other hand there are a couple of freeware alternatives to Hyperterminal including the open source tera term and putty, both for Windows based operating systems. For other operating systems or for commercial equivalents (which tend to be far more comprehensive and complete in their implementation, which is handy if your looking for anything more complicated than a straight ssh/vt100 implementation) you might want to look through the links in the right hand column.

Automatic Teller Machine

Outside of military, government and research usage, some of the world earliest users of large scale computers were the financial and banking sectors of the Western World. The beginnings of computerization in the financial industry can be traced back the early 1950’s and in particular to the Bank of America’s sponsorship of the ERMA (Electronic Recording Method of Accounting) project at the Stanford Research Institute. Designed to automated the banks checking account systems that project was revolutionary and delivered the Bank of America a decisive edge over it’s competitors by streamlining the processing of the many thousands of customer checks it handled on a daily basis. A vital component of the project was the development of MICR or Magnetic Ink Character Recognition, a system for encoding characters at the bottom of checks and documents that was both readable by customer and computers, you can still see this system in use today. The ERMA systems were first placed into service in the late 50′s and continued to be used well into the 1970s, a period which saw the Bank of America grow to become the largest banking organizations in the world.

With the advantages of computerization in the financial and banking industry plain for all to see competitors all over the world gradually began adopting computerised systems to improve the management of their core businesses. The industry placed high demands on the abilities of systems and software in terms of speed, accuracy, reliability and uptime.  They required that a system should be able to continue to operate despite hardware and software failures (fault-tolerant) and that it should be expandable in order to maintain a high transaction throughput as demand increases. In modern times two main players emerged to meet these challenges; Stratus Technologies and Tandem Computers.

Tandem

Tandem Computers were an American systems manufacturer founded in the 1970′s, responsible for producing an early high reliability system in the form of the T/16 platform. Sharing a design influence with a popular Hewlett Packard minicomputer of the era, the HP3000, the T/16 was later renamed to ‘NonStop’ to emphasize it’s focus on reliability. Powering this system was Tandem’s own operating system called Guardian OS which featured fail-safe transaction processing, allowing a program to fail and resume an operation without any loss of data, a highly valued feature in the world of finance and banking. On the hardware front Tandem systems boasted a level of redundancy in terms of components such as multiple CPUs, the I/O bus and memory.  These parts, for example the CPU’s, would contribute to the operation of the computer, however upon detecting a failure the faulty module could shut itself down whilst the system would compensate and continue to operate. Tandems’ design was such that a faulty module could be replaced whilst the machine continued to operate.

Tandem also introduced a fibre optic system called FOX that allowed you to link up to 14 systems (either the NonStop’s successor, the NonStop II, or a later model known as the TXP) . This modularity proved popular in the marketplace, allowing Tandem customers to easily expand their systems as demand within their organization grew. Sometimes, this expansion could be accomplished without needing to shut down the system, an extremely attractive proposition for an organization demanding as close to 100% uptime as possible. The Guardian OS was able to manage the linked systems, handling the failover of all tasks assigned to a faulty server on the network without loss of data.

The NonStop systems received continuing improvements in speed and performance throughout 1980’s and 90’s with little change to the basic underlying redundant architecture. In 1991 Tandem started using the MIPS Computer Systems R3000 microprocessor. In 1997 Tandem was acquired by Compaq who in turn were acquired by Hewlett Packard 5 years later. It is under the HP marque that the NonStop range (now based on an Intel processor) continues to be sold and marketed.

In terms of dumb terminals Tandem systems used either an IBM 3270 terminal or their own proprietary 6530 terminal to access NonStop systems. Today, where there is a requirement for these terminals, most have been replaced with software emulations provided by packages such as OutsideView, Attachmate and TTWin.

Stratus

Stratus, the other main operator in the high reliability marketspace, released their first system in 1982, the Stratus/32, or FT200 as it was later became known. The FT200 used Stratus’s own operating system, VOS (Virtual Operating System), a fault tolerant operating system designed to deliver maximum uptime. Stratus systems typically found homes in industries where reliability was key such as healthcare, financial institutions, securities and exchanges.  The company’s website boast updates of it’s servers uptime levels, often shown to be around 99.9999%. A system which experiences 99% uptime will still experience close to 4 days offline over the course of a year, something which would obviously be unacceptable for a financial institution.

In 1984 Stratus released the XA400 & XA600 and continued to release newer models in the XA series based on the Motorola MC68000 series of microprocessors. In 1991 they released first of the Intel i860-based system. In 1995 Stratus released the Continuum Product line using the Hewlett Packard “PA-RISC” architecture. The Continuum systems and V Series are still maintained by Stratus today. The VOS operating system has also evolved from a proprietary operating system to the release of OpenVOS in 2008.

Initially the VOS based systems required the use of a proprietary Stratus terminal to interface with the system. The 2 most popular terminals were the V102 and the V103, both of which are very similar to the TeleVideo 955 terminal. Stratus also released a v105 terminal based on the DEC VT220. Again, the physical terminals on these devices have more often that not been retired in favor of software emulators such as Procomm and TTWin which are capable of handling the specialized requirements of Stratus terminals.

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more reading: http://www.sri.com/about/ermastory.html

(An interesting aside, another operating systems evolved out of the Multics project, essentially being cut down version of the Multics Operating System. It was named, jokingly at first, UNICS, that being ‘Multics without the balls’. That name stuck and lives on as Unix, while few people have heard of Multics.)

The first Prime computer the Prime 200 was produced in 1972, subsequently in 1973 and 1974 the Prime 300 and Prime 400 were released.  As was common in that era, there was a significant performance improvement and much technical innovation from one model to the next.  This was particularly important to areas such as CAD that constantly demanded larger machines to do ever more sophisticated tasks in this regard Prime proved itself to be very effective.

The early Prime machines were based on the Honeywell 316 and 516 systems and ran a proprietary operating system called DOS or PRIMOS.  The machines were aimed at the technical market and were widely used in universities and organizations such as Ford in their Computer Aided Design area.

As Prime developed ever more capable and powerful machines it also enhanced the operating system to match, something like 20 versions each with Sub-Version of PrimOS were released.  One attractive thing about the Prime range of systems was that the operating system could run unaltered across the entire range.  Prime was also an early adopter of networking and this made it an attractive option to Ford.  Over time Ford used Prime extensively throughout the world and into its suppliers and engineering contractors.

Prime was very successful in the 70s and early 80s and made its way into the fortune 500 group of companies.  By the late 80s and early 90s Prime had began to run out of steam with users demanding ever more processing power per dollar and Prime not able to keep the development up with the demand.  Increasingly lower cost systems were able to deliver the performance looked for with the attendant loss of customers.

While Prime had developed solutions in other fields, many of Prime’s successful offerings were CAD based.  In order to regain some of its dominance Prime purchased a number of CAD companies.  Unfortunately the cost of this left the company vulnerable to a hostile takeover, and an attempt was made to do just that. Prime was put back into private ownership by a venture capitalist J.H. Whitney who ultimately split the company shut down the manufacturing and design parts keeping the CAD solutions.  The remainder of the company specifically the CAD part was later sold to Parametric Technologies who are still around today.

During its heyday prime had a significant presence in the marketplace and competed head to head with the likes of DEC.  One of its most successful marketing campaigns was run in 1980 using actors Tom Baker and Lalla Ward as their Dr Who characters (see this post)

Like many companies of the era, Prime had its own unique approach which included its own Operating System, hardware and range of terminals including the Prime PT200 and PT250.  Many of its users continued to use the Prime machines well after the company ceased to exist switching to Terminal Emulation as the terminals died.  Ultimately the cost of maintaining these systems and the ready availability of very powerful systems for a fraction of the cost of the original machine dealt the death blow to even these systems.

Digital's VT100 terminal

During the heyday of mainframe computing Digital Equipment Corporation (DEC) was one of the most  successful manufacturers of host systems, second only to IBM. DEC produced popular systems such as the PDP-XX, VAX and MicroVAX and, in order to service the needs of these hosts, they also produced a complimentary range of proprietary terminals. The first of these video terminals, the VT05 (the VT, strangely enough, stands for Video Terminal) was released to market in 1970 and had very limited capability, essentially being a ‘glass teletype’ terminal. It also had a huge footprint,  and a design which would have been quite at home on the set of 2001: A Space Odyssey.

Five years later The VT05 and was replaced by the similarly sized VT52. Like many terminals of the day The VT52 was controlled by the manufacturer’s own proprietary control codes, or escape sequences, which were used to control things like cursor movement, deletion,  formatting and so on.

In the late 1970′s the American Nation Standards Institutes defined a standard for escape sequences referenced by the X3.64 standard. The VT100, released by DEC in 1978 was the companies’ first ANSI compliant terminal (though it did provide backward compatibility with the earlier VT52).  On the strength of the companies host systems sales and  the number of developers writing business applications taking advantage of new terminals’ features the VT100 became extremely successful. Many of these applications were also ported to other Unix based systems further adding to the popularity of the VT100. Soon other major terminal competitors, such as Wyse, included the VT100 emulation within there own units.

The VT100 architecture served as the foundation for further development and enhancement culminating in the release of its successors the VT220, VT300, VT420 and VT500 series. Some of the enhancement options made available to the various models included graphics, color, multi-session and multi-national character set support.

In the world of terminal emulation software the VT100 and successors (particularly the VT220) are a staple of many products. In fact unless your terminal emulator specializes in something like a IBM5250 or IBM3270, it is pretty much guaranteed to include a VT100 terminal. Hyper Terminal, installed by default in editions of Microsoft Windows up to an including Windows XP, included the VT52, VT100 and various other emulations. It was capable of modem and telnet connection to hosts. ( If you’re looking for a Hyperterminal replacement any of the free or commerical terminal emulators listed on the right will suffice )

For a more detailed history of the VT100 and DEC terminals in general head on over to http://VT100.net/vt_history

The IBM 5250 terminal was similar to its cousin the  IBM 3270 Information Display System (or 3270 terminal). It connected to the host system using the proprietary IBM SNA protocol via a Twinax cable (coax type cable). It  implemented block mode communication like the 3270, however the two terminals where not compatible. While the IBM 5250 had its own version of block mode and the SNA protocol, from the users prospective the 5250 Display Stations presented the display just like the mainframe screens of the 3270 terminal. Data was still clearly presented in ‘fields’ that the user could easily navigate and input date. The terminal response was quick thanks to all inputted data being buffered locally and then transmitted when the user hit enter. The 5250 gave the user more information about the terminal status, for example a busy indicator would let the user know that the terminal is still waiting for the host to respond. The 5250 came with a color screen and also had a mechanical feedback keyboard that made a clicking sound as you pressed each key in order to simulate the feel of the typewriters of the day. (Side note: Funnily enough the  ‘clicky’ PC equivalent of this type of keyboard, the model M, remains highly sought after although it obviously doesn’t support USB. Here’s a nice modern equivalent which does.)

The 5250 was able to connect to a succession of midrange systems starting with the System/3, and continuing with it’s descendants the System/32, System/34, System/36, System/38, AS400 and the iSeries.

By the time IBM released the AS/400 in 1988, IBM had sold over 250,000 of their System/3x series systems since the release of the System/34 in 1977, making it the most widely used range of midrange systems. The AS/400 series later morphed into the iSeries and the System i, with most users of the older hosts upgrading to the newer and faster offerings. This in turn increased the popularity of the 5250 terminals.

It took some time before PC based terminal emulation really started to encroach on the territory of the physical 5250 terminals range. Historically, as was the case with many other systems, terminals began to disappear as the cost of PC’s dropped and they become ubiquitous in the business environment. Operators began to rationalize their host connectivity solutions and do away with having more than one systems taking up desktop real estate.

However because IBM’s midrange systems communicated via the SNA protocol, ‘gateway’ solutions were deployed on PC networks to facilitate connections between PC’s running terminal emulation software, typically on a TCP/IP network and the SNA host. These offered an alternative to physical terminals or the use of hardware emulation cards in every PC connecting to the host. The SNA gateway that was connecting to the host acted both to manage the client connection and as a protocol converter between the SNA host and the TCP/IP client, allowing the PC running 5250 terminal emulation software to communication with the host system.

There where several different flavors of SNA Gateways released by different companies, such as IBM, SCO and Microsoft to name but a few. Microsoft’s SNA Gateway was widely used because it  allowed the user to choose the Emulation vendor that best suited their requirements. For example you could use the emulation that came with the MS SNA gateway or a 3rd party MS SNA compatible client like TTWin.

Eventually IBM introduced the TN5250 protocol, the 5250’s version of Telnet, operating over TCP/IP. This really was the nail in the coffin for the physical 5250 terminal and opened up the emulation market, eliminating the need for special PC cards or SNA Gateways and giving rise to a new generation of cheaper terminal emulation software packages.

It should be noted that TN5250 differs from TN3270 and both of these differ from the standard telnet protocol used by most other emulated terminals.

Nowadays System/3x series systems have been retied or upgraded to an AS400 or, more likely, one of the later iSeries systems. Of those systems running a legacy application that requires the 5250 terminal, most would be using a terminal emulation connected via the TN5250 protocol. Some applications have also had a web frontend written for them so that emulation isn’t required at all, while others still have used terminal emulators with API’s or OCX controls to write a web or GUI frontend for an application that requires the 5250 terminal. This option is usually taken because it is cheaper to write an application using a emulators OCX then it is to make changes to the host application.

Like many manufacturers of that era they also produced several models of proprietary terminals, such as the PT250, which is still supported by the occasional terminal emulator today…but that’s not the point of this post. The point of this post is a series of great TV spots from the early 80′s staring the Tom Baker version of Doctor Who!

Prime also ran a series of ads staring their own c-3P0 clone (Albert EinPrime!). These obviously ran in Australia (note the voice over) but probably screened elsewhere too. Not as good as the Tom Baker ads, but then, how can you compete with the Doctor?

TTWin and Teemtalk are two commercial terminal emulators which are capable of emulating a prime terminal.

Wyse 50 terminal

If you had anything to do with a terminal based computing in the 1980′s then no doubt than name Wyse would be very familiar to you. Founded in the early 80′s in in San Jose, California Wyse achieved it’s early fame as a manufacturer of a very successful line of character based terminals terminals. A key feature of the Wyse range of terminals was the ability to adopt numerous ‘personalities’ of other terminals in addition to their own native modes. Wyse terminals sold very well and soon became the terminal of choice for the reseller community largely due to the resellers’ ability to source terminals from the one supplier and cater for the majority of host systems. As the list below shows, the range of competitor terminals that the Wyse products were able to emulate was extensive:

Wyse 50 – available ‘personalities’

• Wyse 50 native mode
• Wyse 100 mode
• Televideo 910/910+ mode
• Televideo 920 mode
• Televideo 925 mode
• Televideo 950 mode
• Hazeltine 1500 mode
• ADDS Viewpoint A2 mode
• Data General DASHER D100/D200 mode
• IBM 3101-1X mode
• Lear Siegler ADM 3A Mode
• Lear Siegler ADM 31 Mode
• Lear Siegler ADM 5 Mode

Wyse 60 – available ‘personalities’

• Wyse 50 mode
• Wyse 50+ mode
• Wyse 60 native mode
• Wyse 75 mode
• Wyse 100 mode
• VT52 mode
• VT100 mode
• Televideo 910/910+ mode
• Televideo 920 mode
• Televideo 925 mode
• Televideo 950 mode
• Hazeltine 1500 mode
• ADDS Viewpoint 60 mode
• PC Term (PC/AT/XT type)
• Data General DASHER D100/D200 mode
• IBM 3101-1X mode
• Lear Siegler ADM 3A Mode
• Lear Siegler ADM 31 Mode
• Lear Siegler ADM 5 Mode

(Sources :wy-50 Display terminal quick reference guide, wy-60 Display terminal quick reference guide)

Wyse released numerous terminals over the years, and while the Wyse 50 and 60 are undoubtedly the most widely used Wyse would also release color and graphics capable terminals such as the Wyse 160, 350, 370 and 99GT, some of which were capable of emulating Tektronix terminals and IBM PC graphics. These terminals would connect to hosts via serial connection (RS-232) either through a serial port on that host, or a serial adapter card such as those manufactured by Stallion, DigiBoard etc. Later terminal servers which connected to the corporate network were used, extending the distance of the terminal deployment. These hardy serial terminals were used in almost every environment from solicitor firms, offices, retail outlets to factory and shop floors; that is, in both clean and dirty environments.

However as personal computers and networking became more affordable, software terminal emulation packages began to appear on the market which included the ability to emulate Wyse terminals (early examples included TUN from Esker, TTWin from Turbosoft and ICE-TCP from J. River, just to name a few). These emulation packages began to replace the character terminals as more and more PC’s were introduced within the workplace environment.  The most popular emulations (ie wy50/60, ANSI, Dec vt100/102) were all available within these software packages and were primarily used within the small server environments such as those running SCO Xenix and SCO Unix.  Other specialist software companies provided the more sophisticated emulations such as IBM 3270/5250, Stratus, Prime, Unisys and Tandem and others which primarily found use in the mini and mainframe environments.

Perhaps sensing a shift in the market during the late 1980′s and early 90′s Wyse entered into the manufacture of desktop computers (IBM compatible PC’s) and initially achieved a measure of success for the company. However with the entry of competing companies such as Dell and Gateway, whose business models bypassed traditional sales channels and dealt directly with the end customer, Wyse was unable to compete and witnessed a decline in sales that ultimately led the company to withdrawal from the PC market place. Wyse returned to their ‘grass root’ business of terminals and monitors and by 1995, having now acquired rival terminal manufacturers Link and Qume, held more than a third of the general purpose computer terminal market.

This particular Wyse thin client, an s30 model, runs Windows CE and is powered by an ARM processor. Other OS choices include a Linux distribution maintained by Wyse, Wyse ThinOS and Microsoft Windows XPe.

In late 1995 Wyse would again change direction and move into the market sector for which they are renowned today. Wyse released the Winterm, a ‘thin client’ which, when combined with a standard VGA monitor, standard PC keyboard and mouse to be attached, was designed to provide the lightweight front end to applications based on a central server.  Running over Ethernet, these units provided the users with higher performance and flexibility and, in my experience, they were predominantly used on factory floors, warehouses and places where a higher degree security was necessary. Thin client display protocols available include HTML, X Window, text terminal emulations (ASCII, ANSI, IBM), Microsoft Terminal Services (RDP) and Citrix (ICA).

Today the promise of desktop virtualization (as developed by virtual environment specialists like VMware, Citrix and Microsoft), Cloud computing and “Software as a Service” are extending the benefits of “thin client” computing. We have come full circle: from centralized computing using terminals, to distributed computing using personal computers and now back to centralized server farms using ‘thin clients’. Ironically it’s not uncommon to see web based terminal emulation software running on a thin client!

IRMA board, judging by the Attachmate logo and the PCI interface, mid 90's vintage.

The IRMA board got a mention in my 3270 post last week and low and behold I’ve just stumbled across an interview with one of the former senior executives at Digital Communications Associates (DCA), the company behind the IRMA board. The interview touches on the product itself, the company’s rise and fall and the history of tech companies in that region during the 80′s. The interview was conducted by techdrawl.com, a site the focuses on all things tech from the south…unfortunately that particular page is coming up 404 just now,  however the interview is hosted on vimeo and survives (below).

A little background – the IRMA board was an early  solution which allowed a PC to function as a 3270 terminal. A hardware solution, it came in the form of an expansion card that connected directly to the coax connection in place of the dumb terminal. These were incredibly popular in the mid 80′s and DCA had something approaching 75%  (or 50% depending on who you listen to!) of the market for this kind of device.

Eventually these were replaced by software emulators and IBM’s release of TN3270 and TN5250 which allowed end users to do away their SNA network and operate strictly with PCs over a single TCP/IP Ethernet network. DCA’s fortunes fell and they were gobbled up by terminal emulation software developer Attachmate in the early 1990s.

Shaky cam alert!

John Yates Interviews Bill Hiller from Terri Thornton on Vimeo.

The IBM System 360/25

First announced by IBM in 1971 it could be connected to the company’s System/370 or System/360 Model 25  mainframe. The 3270 became extremely popular during the 1970’s and later on with the release of the IBM 3090 mainframe in 1985.

There are several key differences to the IBM 3270 terminal when compared to other character cell terminals that are common to UNIX users. The 3270 didn’t use the standard ASCII character set that is used by most computer systems today including Windows and Linux, instead making use of the EBCDIC (Extended Binary Coded Decimal Interchange Code) character set, a legacy from the days when Mainframe systems where programmed via punched cards. EBCDIC was used by all the IBM peripherals at the time – Mainframes system still support EBCDIC, to give backwards compatibility.

The other notable difference between the IBM3270 and most other character cell terminals is that the 3270 uses block mode communication instead of character mode. Block mode has several advantages over character mode communication, especially on the slower connections and slower Mainframes available when released.

With a block mode connection the host will completely draw the screen, populating it with fields in which the required data may be entered. The 3270 terminal will buffer all the data inputted by the user until the user hits the enter key, upon which it will  send all the entered data to the host in one go. Compare this to Character communication where every single character that is typed is sent to the host and then the host echo’s that character back to the terminal screen. This can cause a delay in each character being displayed on the screen, particularly over a slow connection and  it also increases CPU load on the host system.

Block mode was advantageous in that it freed up CPU time on the Mainframe by allowing it to process all the data in one hit, reducing the time spent managing IO.

Block mode also improved the user experience when entering data. Because all data is buffered locally the user can enter that data much faster and see the information on the screen in real time even over a slow remote connection. The down side is that this did create a delay on receiving the next screen after data transmission.

A modern day example of this concept is when you enter information into a web form: The server sends you the initial page and you enter the requested information, however nothing is actually sent to the server until you submit that form. Once the form is submitted, all the information you entered is then sent to the server and only then does the server send you the next screen.

The IBM 3270 terminal started its life with a simple keyboard with no function keys and a monochrome green display. It was that characteristic green display which gave rise to the slang ‘green screen’ which came to refer to not only the 3270 but dumb terminals in general. And this blog, of course.

IBM made several enhancements to the 3270 with the release of several new terminal models, adding 12 function keys and a final model with a total of 24 function keys and 3 PA (‘program attention’) keys.

Enhancements were also made to the screen layout with the release of several models from with improved display dimensions of 12×40 to 24×80, 32×80 and 43×80 characters. Later models allowed for switching between 27×132 & 24×80 modes. Wikipedia provides a nice list of the various models and their display characteristics.

Two of the more notable enhancements to the 3270 were the introduction in 1979 of  the 3279 color display (pictured) and the 3287 color printer. In the same year IBM also introduced the 3270 Kanji Display Terminal supporting more then 11,000 Chinese and Japanese characters.

3279 color display terminal, ibm 3270

All these terminals were connected via the IBM’s SNA (Systems Network Architecture) protocol using a coax cable connected to a terminal control unit 3174 or 3274. The 3274 terminal control unit could connect  up to 32 terminals.

The SNA protocol was very popular way of connecting to mainframe systems right through the 1970’s to 1990’s. In the early 90’s the demand for connecting the PC to the host using a terminal emulator was growing. The popular solution to this problem was to use a hardware emulation card or IRMA board that connected your PC to the SNA network using the same coax that was connected to the 3270 terminal. This method of emulating the 3270 terminal was expensive and as non SNA PC networks come on line it meant duplication of networks, one for PC’s and one for Terminals.

As Ethernet networks became more popular for PC the need to connect users to the host via Ethernet increased. The initial solution to this was an SNA Gateways like Microsoft’s SNA Gateway (Microsoft Host Integration Server). This would allow a user to connect their PC loaded with a terminal emulator to the host over an Ethernet connection via the SNA Gateway.

The main problem with SNA Gateways was that each PC required SNA Gateway client software to be installed locally. Several SNA Gateways were released by different companies such as IBM, SCO and Microsoft, just to name a few. The issue was that each implementation was slightly different and the end user required both a client that matched they gateway and  a terminal emulator that supported that specific SNA Client. This generally meant that once you purchased an SNA Gateway you were locked in to a particular emulation product. Microsoft’s SNA Gateway was widely used, and, while it came with a simple 3270 emulator users that required some of more advance features of the terminal would opt for one of the variety of 3rd party emulators available that supported the Microsoft gateway.

Eventually SNA connectivity lost favor for the TN3270 protocol, the 3270’s version of Telnet. The TN3270 differs from the standard telnet used by other terminal emulations such as the DEC VT, and requires an emulation product that has a telnet capable 3270 emulation.

With most PC networks already using TCP/IP for their Windows networking and the need for expensive emulation cards on a dedicated network removed, IBM3270 emulators also became easier to deploy and manage. The number of IBM3270 emulation products in the market also increased, and making it more cost effective to use emulation in place of the actual terminal.

This lead to the decline in popularity of the physical terminal in the office space, instead emulators like Attachmate Extra, Wall Data’s Rumba, WRQ’s Reflection or Turbosoft’s TTWin filled the gap.

However the physical terminals continued to find a home in some areas sch as manufacturing industries where either users didn’t have the need for the extra range of functions that a PC’ could provide, or alternately, the workspaces were subject to difficult conditions (such as very dusty or harsh environments)  where terminals were much better suited to the kind of day to day abuse they would encounter.

By the end of the 90’s many 3270 terminals had been replaced with emulator software or their host systems had been retired. 3270 emulators still enjoy wide usage today, however in some cases they appear in a more modern guise. For example, embedded behind a web page where the emulator is in the background using a technique called screen scraping. This is where the data sent from the host is captured from the emulator and represented to the user in a different form, in this case, over the web. This is usually done through emulation software that provides an API or OCX control.

Bonus extra: All sorts of hardware and software solutions were thrown up in an effort to bring the PC and the 3270 terminal together over the years.  Witness the IBM 5271, the mutant love child of an IBM XT PC and a 3270 terminal. The 122 key keyboard pictured in the link contains 3270 specific keys and the normal keys you’d expect on a 101 key pc keyboard, all mixed into one. The machine was powered by an 8088 processor and ran at a blazing 4.77 MHz,  just like the original IBM XT.

• The IBM 5271